we write the contents of the hashedPasswordFile into a string to prevent
issues with paths that are used from the host and are invalid on the
deployment target
This also includes some little syntactical fixes.
The commit is needed since colmena works mostly with nix' flake
experiemental feature. It attempts to find a locked version of nixpkgs,
which wasn't there yet. By using the standard name "flake.nix", nix
automatically picks up the file and generates a `flake.lock` if it
doesn't exist yet. This brings us one step closer to a buildable system.
